Make a beginning of parsing GNU date items with nom

[wanderinglethe]

GNU date understands multiple "items", currently uutils date only supports a limited amount of formats.

To support more formats I looked into using nom to parse these items. These items then need to be verified and combined to calculate a single date time.

Since this is my first using nom and I don't have much experience with Rust, please give feedback on style, design.

[sylvestre]

would be nice to have examples

[wanderinglethe]

Didn't knew I committed this file, not really sure if we should add this because it's straight out of the GNU docs.

Although I guess we can have some supported GNU features in the documentation.
And maybe some tracking issue for all GNU features.

[sylvestre]

I guess you saw:

---- parse_items::items::tests::some_items stdout ----
thread 'parse_items::items::tests::some_items' panicked at 'assertion failed: `(left == right)`
  left: `Ok([TimeZoneRule(TzIdentifier("Europe/Amsterdam")), SecondsEpoch(SecondsEpoch { seconds: 123, nanoseconds: 456000000 }), CalendarDay(RawCalendarDay { day: 14, month: 11, year: 2022 }), MonthDay(RawMonthDay { day: 14, month: 11 }), TimeOfDay(RawTimeOfDay { hours: 12, minutes: 34, seconds: 45, nanoseconds: 789123456 }), TimeZoneCorrection(TimeZoneCorrection { hours: 1, minutes: 30 }), TimeOfDay(RawTimeOfDay { hours: 23, minutes: 0, seconds: 0, nanoseconds: 0 })])`,
 right: `Ok([TimeZoneRule(TzIdentifier("Europe/Amsterdam")), SecondsEpoch(SecondsEpoch { seconds: 123, nanoseconds: 456000000 }), CalendarDay(RawCalendarDay { day: 14, month: 11, year: 2022 }), MonthDay(RawMonthDay { day: 14, month: 11 }), TimeOfDay(RawTimeOfDay { hours: 12, minutes: 34, seconds: 56, nanoseconds: 789123456 }), TimeZoneCorrection(TimeZoneCorrection { hours: 1, minutes: 30 }), TimeOfDay(RawTimeOfDay { hours: 23, minutes: 0, seconds: 0, nanoseconds: 0 })])`', src/parse_items/items.rs:76:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[sylvestre]

Suggested change

	nom = "7.1"
	nom = "7.1"

[sylvestre]

Looks but could you please update the README?
Will it be possible to manage cases like?

 date -d@1687977240
date: invalid date '@1687977240'

[sylvestre]

@wanderinglethe ping?

[tertsdiepraam]

I think there's too many macros that could be fairly simple functions. It's not really a problem if tests are a bit verbose :)

[tertsdiepraam]

Will it be possible to manage cases like?

I think we should do this in another PR. I'd like to merge this relatively soon, so we can build further with it.

[philolo1]

@wanderinglethe are you still working on the pr or may i take over it?

[wanderinglethe]

@wanderinglethe are you still working on the pr or may i take over it?

I am sorry @philolo1, I missed your question and wasn't able to participate.